1. Technical Field
The present invention relates generally to motor vehicle evaporative emission control systems and, more particularly, to a system and method of monitoring for the presence of purge flow in a purge system for evaporative emission control in a motor vehicle.
2. Discussion
In recent years, motor vehicle manufacturers have greatly reduced the levels of hydrocarbons, e.g., carbon monoxide, carbon dioxide, etc., and other gasoline and diesel powered motor vehicle emissions in response to increased governmental regulations aimed at preserving and protecting the environment. In addition to the commonly known tailpipe emissions, i.e., the exhaust gases generally produced during the combustion process of the motor vehicle engine, there are also evaporative emissions. That is, a motor vehicle produces emissions while simply sitting parked due to evaporation of oil, fuel and other fluids which are common to motor vehicles.
Governmental regulations such as those promulgated by the Federal Environmental Protection Agency (EPA) and the California Air Resource Board (CARB) often establish strict limitations on the amount of emissions, both exhaust gas and evaporative, that a motor vehicle may produce. Modern day regulations also require that a motor vehicle manufacturer test and certify that the vehicles manufactured and sold conform to these regulations. The allowable amounts of emissions are often measured as parts per million (ppm) of a total sample of air collected.
In this regard, modern motor vehicles incorporate sealed fuel and lubrication systems which commonly include charcoal canisters and the like for collecting vapors produced as a result of the evaporation of hydrocarbon based fluids. The conventional sealed fuel and lubrication systems typically retain the vapors for later burning in the vehicle engine when the vehicle engine is running. Any vapors not collected by such systems and emitted from the motor vehicle into the environment are generally classified as evaporative emissions.
In particular, evaporative emission control (EEC) systems prevent the escape of gasoline vapors from the fuel tank and carburetor, whether or not the engine is running. Such evaporative emission control systems commonly utilize an activated charcoal canister to trap the vapors. Modern automotive purge systems commonly employ an electronic controlled solenoid valve which permits manifold vacuum to purge evaporated emissions from the charcoal canister. On restarting of the engine, a purge system causes a flow of filtered air through the canister to purge vapors from the charcoal canister. The air flow mixture of air and vapors then generally passes through one or more tubes leading to the engine for burning in the engine.
Current and future proposed regulatory requirements include a rational check of the purge system flow to determine if the purge system is functioning properly as required. In order to meet the evaporative regulatory standards, a purge system flow monitor is needed to monitor and test the operation of the purge system. In the past, some flow monitor systems provided a rationality check of the electronic controlled solenoid valve. This type of test has generally been limited to determining whether the electronic controlled solenoid valve is electrically energized or deenergized. Other proposed purge monitor systems may require additional emissions system hardware. However, the use of additional hardware adds to the overall cost and complexity of the purge system.
It is therefore one object of the present invention to provide for a system and method for monitoring purge flow to insure that a purge flow system is operating properly.
Another object of the present invention is to provide for a flow monitor system and method of monitoring evaporative emission control purge flow in a motor vehicle while requiring minimal hardware.
Yet, a further object of the present invention is to provide for a purge flow monitor which accurately tests the purge flow in a motor vehicle in a low cost and efficient manner to insure that the evaporative emission control purge flow system is operating properly.